If you are wiring a shed, installing a new air conditioner, or simply replacing a power point, understanding cable sizes is critical. In Australia, using the wrong cable size isn't just inefficient—it is a fire hazard and a breach of the Wiring Rules (AS/NZS 3000).
Here is everything you need to know about choosing the correct cable size for your job. In Australia, we use the metric system for cross-sectional area (mm²). A common mistake is thinking "thicker wire is always better." While thicker wire reduces resistance, it is more expensive and harder to terminate. cable sizes australia
This guide is for educational purposes and does not replace a site-specific calculation by a qualified professional. Disclaimer: This information is based on general AS/NZS 3008 guidelines as of 2025. Actual installation depends on derating factors, insulation types, and specific site conditions. Hire a licensed professional. If you are wiring a shed, installing a
Voltage drop between the point of supply and the equipment must not exceed 5% for general power (230V → 218.5V) or 8% for lighting (230V → 211.6V). In Australia, we use the metric system for
| Conductor Size (mm²) | Typical Current Rating (Clip-on) | Common Australian Applications | | :--- | :--- | :--- | | | 10 Amps | Lighting circuits (rarely used now; most use 1.5mm) | | 1.5 mm² | 15 Amps | Standard lighting circuits, smoke alarms. | | 2.5 mm² | 20-25 Amps | General Power Outlets (10A GPOs). Standard home power circuit. | | 4.0 mm² | 32 Amps | Dedicated circuits: Ovens, cooktops, large air conditioners (up to 7kW). | | 6.0 mm² | 40-50 Amps | Instantaneous hot water, induction cooktops, sub-mains to a shed (short run). | | 10 mm² | 65 Amps | Small sub-mains (garage/granny flat), large commercial ovens. | | 16 mm² | 85 Amps | Main switchboard upgrades, EV chargers (high power), large sub-mains. | The Killer: Voltage Drop You can install a 2.5mm² cable rated for 20 amps, but if you run it 80 meters to a shed, your tools will overheat and fail.